The Boston Obesity/Nutrition Research Center represents a collaborative program established by investigators at the New England Medical Center, the Beth Israel Hospital, the Deaconess Hospital, the Harvard School of Public Health, and the Boston University School of Medicine. These 40 investigators have a record of collaboration and scientific productivity which justify the creation of this Center. The research base of this application comprises 25 RO-1 grants (and numerous other grants from various sources) which focus on obesity, energy metabolism, or other nutritionally related diseases. The program also contains 5 NIH research training grants. The Principal Investigator has an established record in the study of obesity, and extensive experience as a leader of collaborative interdisciplinary research. The principal themes of the Boston Obesity/Nutrition Center are: 1) the natural history of obesity, 2) energy metabolism in obesity, healthy control subjects and other nutritional diseases, and 3) education and training. To address these themes, the Center will support Pilot and Feasibility Studies, an Enrichment Program, and Core Laboratories. The Core Laboratories include Epidemiology, Clinical/Metabolic, Body Composition/Energy Expenditure, Cellular Biochemistry/Signal Transduction, and Transgenic Cores. Support for the Boston Obesity/Nutrition Research Center will also allow senior faculty to direct the training of the many young investigators emerging from the affiliated institutions into obesity research. The members of the Center believe that these elements will assure the cross-disciplinary collaboration and interaction between investigators necessary to improve our understanding of the origins, pathophysiology and therapy of obesity.